Sequels often disappoint, but HM Treasury is no ordinary second-time author. So it was Chancellor Gordon Brown and his most senior lieutenants who last week launched the 'Gold Book' - formal title Microeconomic Reform in Britain - at No 11 Downing Street.

Few things normally distract the Treasury's army of boffins in the week before a Budget. But they were extremely animated about this dry, semi-academic tome, and with good reason, because unfathomable economics has become the lingua franca of Whitehall. And this book is the first to map it spreading to every corner of British policymaking - from immigration to university reform and road-charging.

It is the follow-up to the Silver Book - Reforming Britain's Economic and Financial Policy - which explained how five years of Treasury economic genius had protected Britain from any serious macroeconomic problems and established what is widely considered to be best practice in world macro policy.

That success, which included granting the Bank of England the power to set interest rates, left the boffins of Great George Street twiddling their thumbs. As Ed Balls, the Treasury's chief economic adviser, once commented: 'Bank independence has liberated us.'

The Treasury used to spend about half its time attempting to establish what the appropriate interest rate was, so this new book illuminates exactly how it has prevented mass redundancy since Brown outsourced interest rate decisions. Now it busies itself with anything that might affect Britain's long-run productivity potential: from immigration to regional policy, planning law and higher education funding.

And, as Balls explained last week, the basic strategy behind health and education, and criminal justice reform, is informed by the hitherto happy experience of Bank of England independence.

He calls this 'constrained discretion' - basically, that the Treasury should set a target, then devolve power to technical experts who are equipped to meet it.

Mindful of the maxim that knowledge is power, the Treasury has sought intellectual leadership in microeconomics. The majority of economists who work in the Treasury now work on micro matters. Brown's department has also co-opted a fair number of Britain's leading economics brains into government reviews, quangos and commissions.

As London School of Economics Professor Nick Crafts suggests, the book vividly shows how important the academic economic mindset is in the Treasury, but is that mirrored elsewhere in government activities?

'We're trying to get more economists into other departments,' says the Treasury's most senior civil servant.

The Government Economic Service has doubled in size since Labour came to power, as departments seek some intellectual balance to the Treasury cost-benefit analyses, risk transfers and market failures. But the Treasury operates outside the rest of government. It recruits entirely separately from the normal civil service process.

The process of writing the book has helped the Treasury to distil lessons and strategies that are applicable across government. The result could be a revolution in British policymaking. Radical ideas such as pricing the airwaves, airport landing slots, scrapping the Common Agricultural Policy, and even the Green Belt could force their way up the agenda on economic grounds.

But what about the disagreements at the heart of the academic discipline? Doesn't the policy prescription depend on the sort of economic theory that you follow?

'We're exploiting the consensus that exists in economics,' says O'Donnell. 'It does provide you with a way of thinking.'

Perhaps economics has achieved what generations of Sir Humphreys have tried and failed to do. The dismal science may have become the ultimate way of depoliticising politics.